Remote control of enzyme selectivity: the case of stevioside and steviolbioside

The remote control of lipase PS site- and regioselectivity by substrate modification has been observed in the acetylation of stevioside (1) and steviolbioside (2): deglucosylation at position C-19 changed the acylation site of the sophorose moiety linked at C-13. In fact, while esterification of 1 gave mainly the corresponding 6''-O-acetylated derivative, acylation of 2 gave exclusively the 6'-O-monoester. A possible rationale has been suggested, based on the conformational behavior of the substrates in different simulated solvents. (C) 2003 Elsevier Ltd. All rights reserved.